Metallicity estimation versus stellar mass. The big magenta circle, red and blue stars correspond respectively to DB, LAEs and SFRs with EW_rest−frame(Lyα) < 20 Å in our sample. Thin green upper limits and the green square are the data points from Nakajima et al. (2012a,b), small grey dots are Xia et al. (2012) values for z > 1 emitting galaxies. Black long-dashed, solid, dashed and dotted-dashed curves are the M_∗ − Z relations from Maiolino et al. (2008) for the labeled redshifts. The horizontal solid line indicates solar metallicity (12+log (O/H) = 8.7).